Published German patent document DE 103 05 656 describes a method and a device for controlling an internal combustion engine, in which method, based on the comparison between a first cylinder-specific variable characterizing the combustion process in at least one cylinder and a setpoint value for this variable, an actuating variable of an actuating element is used to influence at least one selected actuating variable. The output signal of a structure-borne noise sensor is used to form the variable. On the basis of the signal from a structure-borne noise sensor, a feature is obtained in this case which is adjusted to a predefined setpoint value.
Cylinder-specific variables that may characterize the combustion process in at least one cylinder are able to be obtained on the basis of a combustion chamber pressure sensor as well. Starting from a structure-borne noise sensor and/or a combustion chamber pressure sensor, various features that characterize the combustion process in at least one cylinder may be obtained and used for the control.
So-called homogeneous and/or partly homogeneous combustion methods may be used in the future in directly injecting combustion engines, e.g., in diesel engines, in order to markedly reduce the particle and nitrogen oxide emissions. The precise observation of a predefined combustion characteristic will be required to comply with emissions, noise and specified consumption requirements. To this end, as described in the above related art, a characteristic quantity characterizing the combustion process is determined on the basis of a cylinder-pressure measurement and/or a structure-borne noise measurement. Hereinafter, this characteristic quantity is also referred to as feature.
The sensor technology and signal conditioning involved in this context, especially for detecting the pressure variables, are cost-intensive. Therefore, there is a need to minimize the cost while simultaneously preserving the advantages of a corresponding closed-loop control and/or open-loop control.